The fifth volume of the dictionary, covering "slab" to "zydeco", is out in March from Harvard University Press. It completes a project begun in 1962 at the University of Wisconsin-Madison, when Fred Cassidy was appointed chief editor of a dictionary of American dialects. Cassidy spent several years crafting a 1,600-question survey covering all aspects of daily life, and in 1965, 80 fieldworkers set out in "word wagons" to 1,002 communities across the US, interviewing 2,777 people over six years. This information has been mapped by editors over the last 40 years with written materials dating from the colonial period to the present, creating a 60,000-entry dictionary that its chief editor says gives the lie to the popular myth that American English has become homogenised by the media and the mobility of America's population.

"There is still a tremendous amount of regional variation," said Joan Houston Hall. "Yes, of course the language has changed: it's the nature of language to change. But it doesn't change in the same ways or at the same pace across the country. And although some local words get pushed out by nationwide commercial terms, new ones come into the language. They are the kinds of words we use with family and friends rather than those we learn at school, and often we're not aware that other people aren't familiar with them."

Some of Hall's favourite terms from the fifth volume, which runs to over 1,200 pages, include whoopensocker (something extraordinary of its kind, especially a large or strong drink, chiefly used in Wisconsin), willywags (a New England term for an area with tangled underbrush), upscuddle (southern Appalachian term for a noisy quarrel), strubbly (Pennsylvania German term for untidy) and swivet (a term for a state of anxiety from the South). A slough pumper is the Minnesota term for a bittern, because it lives in sloughs or marshes and makes a noise like an old wooden pump, a tolo is the Washington State word for a dance to which women invite men, and to "tump over" is to knock something over in the South.

The dictionary shows how different regions of the US refer to the same item in various ways: fluff under the bed is described as dust kitties in the Northeast, dust bunnies in the Midwest, house moss in the South and woolies in Pennsylvania, while a sandwich will be a po'boy in Louisiana, but a hoagie, sub, grinder, hero, or torpedo elsewhere. A description of a remote place, meanwhile, can range from the boondocks to the puckerbrush, the tules, or to Hall's favourite, the willywags.

"A friend told me this weekend that when he starts browsing the pages of DARE, he gets seduced by the next entry, and the next, and pretty soon he looks up to discover that an hour has gone by. I find the same thing, and I've read all this many times over," said Hall. A digital edition of the dictionary will launch next year, allowing the team to update the text on a regular basis and add new entries.